Dirk Koester

Neural circuits of hierarchical visuo-spatial sequence processing

Sequence processing has been investigated in a number of studies using serial reaction time tasks or simple artificial grammar tasks. Little, however, is known about higher-order sequence processing entailing the hierarchical organization of events. Here, we manipulated the regularities within sequentially occurring, non-linguistic visual symbols by applying two types of prediction rules. In one rule (the adjacent dependency rule), the sequences consisted of alternating items from two different categories. In the second rule (the hierarchical dependency rule), a hierarchical structure was generated using the same set of item types. Thus, predictions about non-adjacent elements were required for the latter rule. Functional Magnetic Resonance Imaging (fMRI) was used to investigate the neural correlates of the application of the two prediction rules. We found that the hierarchical dependency rule correlated with activity in the pre-supplementary motor area, and the head of the caudate nucleus. In addition, in a hypothesis-driven ROI analysis in Brocas area (BA 44), we found a significantly higher hemodynamic response to the hierarchical dependency rule than to the adjacent dependency rule. These results suggest that this neural network supports hierarchical sequencing, possibly contributing to the integration of sequential elements into higher-order structural events. Importantly, the findings suggest that Brocas area is also engaged in hierarchical sequencing in domains other than language.

Morphosyntax, Prosody, and Linking Elements: The Auditory Processing of German Nominal Compounds

The morphosyntactic decomposition of German compound words and a proposed function of linking elements were examined during auditory processing using event-related brain potentials. In Experiment 1, the syntactic gender agreement was manipulated between a determiner and the initial compound constituent (the nonhead constituent), and between a determiner and the last constituent (head). Although only the head is (morpho)syntactically relevant in German, both constituents elicited a left-anterior negativity if its gender was incongruent. This strongly suggests that compounds are morphosyntactically decomposed. Experiment 2 tested the function of those linking elements which are homophonous to plural morphemes. It has been previously suggested that these indicate the number of nonhead constituents. The number agreement was manipulated for both constituents analogous to Experiment 1. Number-incongruent heads, but not nonhead constituents, elicited an N400 and a subsequent broad negativity, suggesting that linking elements are not processed as plural morphemes. Experiment 3 showed that prosodic cues (duration and fundamental frequency) are employed to differentiate between compounds and single nouns and, thereby, betwen linking elements and plural morphemes. Number-incongruent words elicited a broad negativity if they were produced with a single noun prosody; the same words elicited no event-related potential effect if produced with a compound prosody. A dual-route model can account for the influence of prosody on morphosyntactic processing.

The morphosyntactic decomposition and semantic composition of German compound words investigated by ERPs.

In two experiments, we investigated the morphosyntactic decomposition and semantic composition of acoustically presented German compound words. A left-anterior negativity (LAN) was found in the ERP for gender incongruent, initial compound constituents although these constituents are syntactically irrelevant in German. This LAN provides online evidence for morphosyntactic decomposition. Experiment 1 showed also preliminary evidence for semantic composition, which was further investigated in Experiment 2 by comparing semantically transparent and opaque compounds. Transparent compounds elicited an increased negativity with a centroparietal maximum that occurred during the presentation of the head constituent. This negativity is suggested to reflect the semantic integration of compound constituents that is necessary after the constituents have been accessed separately.

Motor expertise modulates the unconscious processing of human body postures

Little is known about the cognitive background of unconscious visuomotor control of complex sports movements. Therefore, we investigated the extent to which novices and skilled high-jump athletes are able to identify visually presented body postures of the high jump unconsciously. We also asked whether or not the manner of processing differs (qualitatively or quantitatively) between these groups as a function of their motor expertise. A priming experiment with not consciously perceivable stimuli was designed to determine whether subliminal priming of movement phases (same vs. different movement phases) or temporal order (i.e. natural vs. reversed movement order) affects target processing. Participants had to decide which phase of the high jump (approach vs. flight phase) a target photograph was taken from. We found a main effect of temporal order for skilled athletes, that is, faster reaction times for prime-target pairs that reflected the natural movement order as opposed to the reversed movement order. This result indicates that temporal-order information pertaining to the domain of expertise plays a critical role in athletes’ perceptual capacities. For novices, data analyses revealed an interaction between temporal order and movement phases. That is, only the reversed movement order of flight-approach pictures increased processing time. Taken together, the results suggest that the structure of cognitive movement representation modulates unconscious processing of movement pictures and points to a functional role of motor representations in visual perception.

The functional role of working memory in the (re-)planning and execution of grasping movements.

Three experiments were conducted to dissociate movement planning costs and movement execution costs in working memory (WM). The aim of the study was to clarify what kind of WM processes (verbal, spatial, or both) are recruited during movement planning and movement execution. Therefore, a WM task (verbal and spatial versions) was combined with a high-precision manual action. Participants initially planned a placing movement toward 1 of 2 targets, subsequently encoded verbal or spatial information in WM, and then executed the movement during the retention phase. We tested the impact of movement execution on memory performance (Experiment 1), the role of WM task difficulty as a moderating variable in motor-memory interactions (Experiment 2), and the impact of implementing a new motor plan during memory retention (Experiment 3). Our results show that movement execution disrupted spatial more than verbal memory (Experiment 1) and that this domain-specific interference pattern was independent of WM task difficulty (Experiment 2). Hence, the results of Experiments 1 and 2 demonstrate that executing a prepared movement recruits domain-specific visuospatial memory resources. Experiment 3 involved trials that required the implementation of a new motor plan. The additional planning requirement during the retention phase reduced performance in both WM tasks in equal measure beyond the relative movement execution costs observed in Experiments 1 and 2. These results provide evidence for distinct roles of WM in manual actions, with action execution requiring principally modality-specific capacities and (re-)planning engaging modality-general WM resources.

Mental representation and motor imagery training

Research in sports, dance and rehabilitation has shown that basic action concepts (BACs) are fundamental building blocks of mental action representations. BACs are based on chunked body postures related to common functions for realizing action goals. In this paper, we outline issues in research methodology and an experimental method, the structural dimensional analysis of mental representation (SDA-M), to assess action-relevant representational structures that reflect the organization of BACs. The SDA-M reveals a strong relationship between cognitive representation and performance if complex actions are performed. We show how the SDA-M can improve motor imagery training and how it contributes to our understanding of coaching processes. The SDA-M capitalizes on the objective measurement of individual mental movement representations before training and the integration of these results into the motor imagery training. Such motor imagery training based on mental representations (MTMR) has been applied successfully in professional sports such as golf, volleyball, gymnastics, windsurfing, and recently in the rehabilitation of patients who have suffered a stroke.

The costs of changing an intended action: movement planning, but not execution, interferes with verbal working memory.

How much cognitive effort does it take to change a movement plan? In previous studies, it has been shown that humans plan and represent actions in advance, but it remains unclear whether or not action planning and verbal working memory share cognitive resources. Using a novel experimental paradigm, we combined in two experiments a grasp-to-place task with a verbal working memory task. Participants planned a placing movement toward one of two target positions and subsequently encoded and maintained visually presented letters. Both experiments revealed that re-planning the intended action reduced letter recall performance; execution time, however, was not influenced by action modifications. The results of Experiment 2 suggest that the actions interference with verbal working memory arose during the planning rather than the execution phase of the movement. Together, our results strongly suggest that movement planning and verbal working memory share common cognitive resources.

When bicycle pump is harder to read than bicycle bell: effects of parsing cues in first and second language compound reading

Reading and understanding morphologically complex words can sometimes be a particular challenge to nonnative speakers. For example, compound words consist of multiple free morphemes, oftentimes without explicit marking of the morpheme boundaries. In a lexical decision task, we investigated compound reading in native and nonnative speakers of Dutch. The compounds differed in that the letter bigram that formed the morpheme boundary could or could not occur within a Dutch morpheme, thus providing an orthotactic cue as to the position of the morpheme boundary. Native and nonnative speakers responded faster to compounds that contained such an orthotactic cue. Additional analyses showed that although native speakers used this cue for long, but not for short compounds, no such word length modulation was observed for nonnative speakers. It is suggested that orthotactic parsing cues are used during compound reading and possibly even more so in nonnative speakers.

Event-related brain potentials during the monitoring of speech errors

When we perceive speech, our goal is to extract the meaning of the verbal message which includes semantic processing. However, how deeply do we process speech in different situations? In two experiments, native Dutch participants heard spoken sentences describing simultaneously presented pictures. Sentences either correctly described the pictures or contained an anomalous final word (i.e. a semantically or phonologically incongruent word). In the first experiment, spoken sentences were task-irrelevant and both anomalous conditions elicited similar centro-parietal N400s that were larger in amplitude than the N400 for the correct condition. In the second experiment, we ensured that participants processed the same stimuli semantically. In an early time window, we found similar phonological mismatch negativities for both anomalous conditions compared to the correct condition. These negativities were followed by an N400 that was larger for semantic than phonological errors. Together, these data suggest that we process speech semantically, even if the speech is task-irrelevant. Once listeners allocate more cognitive resources to the processing of speech, we suggest that they make predictions for upcoming words, presumably by means of the production system and an internal monitoring loop, to facilitate lexical processing of the perceived speech.

Athletes and novices are differently capable to recognize feint and non-feint actions

Fast motor reactions in sports often require the ability to predict the intended action of an opponent as early as possible. Therefore, the present paper investigates whether beach volleyball athletes are able to recognize different attack hits (i.e. smash vs. poke shot) at an earlier stage of the movement than novices. Beach volleyball athletes and novices took part in a response priming experiment (Experiment 1). Participants had to decide whether a presented target picture depicts a smash or a poke shot. Importantly, the preceding prime pictures were taken from different stages of the movements varying between the jump (beginning of the movements) and the hand-ball contact (end of the movements). Diverging response congruency effects was found for athletes and novices. Athletes were able to recognize at an earlier movement stage than novices which kind of attack hit was shown at the prime picture. It is suggested that athletes might implicitly read movement-related patterns in the depicted athlete’s body posture (e.g. the angle of the elbow). In contrast, novices might use information which is easier to access (e.g. hand-ball relation). In a second experiment, novice participants received a visual training to test for a potential perceptual source of the priming effects. Notably, participants did not improve their ability to differentiate the volleyball techniques, indicating that a better recognition performance in athletes is based on motor and not on perceptual expertise.